Smarter guys than me will respond I am sure but 4500 is probably close to life span expecially in a major gun. I just got a new CK Arms limited thunder 9mm last month with about 500 thru it now and you can ride the slide all the way to the last 1/8" and it will still go into battery easily. I would remove the spring and make sure the slide is smooth all the way, double check the slide where the disconnector engages, and replace the recoil spring. I was curious what # spring is in my gun and was going to send a message and ask.